Technical Abstract:
Many oro-nasal behaviors are considered to be stereotypic and abnormal and have been implicated as an indicator of poor welfare in swine. There is some evidence in other monogastric species to suggest that oral stereotypies serve a pH buffering function and reduce ulceration of the stomach resulting from restricted feeding practices. Stomach ulceration is prevalent in swine and a weak link between stereotypies and ulceration has been established. The objective of this study was to determine whether the incidence or types of oro-nasal behaviors were affected by dietary sodium bicarbonate. Sixteen sows housed in gestation crates were subjected to change in diet for 2 wk of a 6-wk experimental period, with each animal therefore acting as its own control. During wks 1 & 2 and wks 5 & 6, all sows were fed standard commercial ration. During wks 3 & 4, all sows were fed a diet containing 2% sodium bicarbonate but identical to normal diet in other ingredients and total energy content. Behavior and heart rate were recorded on the middle day of each week from 0.5h before feeding to 2h after feeding and analysed to determine incidence and durations of oro-nasal behaviors and heart rate responses to feeding. Sows spent 46.2% of the pre-feeding observation period engaged in oro-nasal behaviors, increasing to 55.23% of the post-feeding period (P<0.05). The main pre-feeding behaviors were nosing the crate (NC = 11.7%) and bar biting (BB = 11.6%). The main post-feeding behaviors were nosing the floor (NF = 22.3%) and sham chewing (SC = 10.2%). The post-feeding durations of BB and NF were both lower after the diet contained bicarbonate (BB wks 1&2 = 330s, wks 3&4 = 166s wks 5&6 = 175s, P<0.01, NF wks 1&2 = 2010s, wks 3&4 = 1412s, wks 5&6 = 1140s, P<0.05), but the post-feeding incidence of nosing the trough (NF) increased (wks 1&2 = 192s, wks 3&4 = 514s, wks 5&6 = 559s, P<0.001). The heart rate response to feeding was higher (p<0.01) in wk 4 (163bpm) than any of the other wks (151 bpm). The results suggest that the addition of dietary bicarbonate may affect both the performance of feeding-related stereotypic behaviors and the cardiac response to feeding. Further investigation is required to elucidate the mechanisms by which bicarbonate may be acting.